1. Field of the Invention
The invention relates to a lens device, more particularly to a lens device provided with a positioning unit that facilitates axis correction of a lens.
2. Description of the Related Art
As shown in FIG. 1 and FIG. 2, a lens device 10 includes a lens barrel 11, and fixed lenses 12, 13 and a primary lens 14 disposed in the lens barrel 11. Since the primary lens 14 has the most sensitive optical characteristics, it is disposed in an outermost end of the lens barrel 11 to facilitate correcting of the position of the primary lens 14 for achieving optimum optical characteristics for the lens device 10. This process is referred to as “axis correction.”
To perform axis correction, the lens device 10 is first mounted on a standard lens device 20 having a plurality of standard lenses 21. When light rays 22 pass through the fixed lenses 12, 13 and the primary lens 14 of the lens device 10, as well as the standard lenses 21 of the standard lens device 20, an image is formed on an imaging region 23. Next, a plurality of lens-adjusting claws 30 are inserted between the lens barrel 11 and the primary lens 14 to move the primary lens 14 in radial directions until the image formed on the imaging surface 23 is clearest. When the axis correction is completed, an adhesive 16 is injected into the gap 15 between the lens barrel 11 and the primary lens 14 to fix the primary lens 14 in the lens barrel 11.
Although axis correction can be performed for the aforesaid lens device 10, the following shortcomings are encountered:
1. A larger conventional lens device 10 presents no difficulty when using the lens-adjusting claws 30 to perform axis correction. However, as required dimensions for lens devices become smaller due to advancements in technology, the alignment-adjusting claws 30 become difficult to operate, thereby resulting in inefficient and inaccurate axis correction.
2. Due to pressure differences, the adhesive 16 can easily flow onto an effective area of the primary lens 14, thus resulting in adverse effects on the optical characteristics of the lens device 10. When the adhesive 16 flows onto the effective area of the primary lens 14, not only do the lens barrel 11 and the primary lens 14 require cleaning, but the axis correction also needs to be restarted, thereby resulting in inefficient axis correction.
3. Due to the gap 15 present between the lens barrel 11 and the primary lens 14, the primary lens 14 can easily dislocate from its corrected position due to the fluidity of the adhesive 16. When dislocation of the primary lens 14 occurs, the axis correction needs to be restarted, thereby making the axis correction process inefficient.